This invention relates to fiber reinforced resin sheets for use in molding composite articles, more particularly it relates to continuous filament fiber reinforced resin sheets.
Composite sheets of continuous filament reinforced resin have been made. One technique is to prepare a warp of filaments as by winding on a frame, impregnating them with resins and hot pressing to form a thin flat sheet which is cut from the frame. Several such sheets are then cross lapped and again hot pressed to form the final reinforced composite product. Such products have high strength and stiffness.
Problems occur when attempts are made to produce deep drawn three dimensional articles by hot pressing continuous carbon, p-aramid or glass filament containing resin sheets. The articles in many instances exhibit uneven areas and wrinkles. The use of staple fibers as reinforcement substantially overcomes the above-stated problems but at a great sacrifice to strength and stiffness.